Devices using oscillator circuits have often depended on compensation circuits to minimize frequency shifts due to variations in the ambient temperature. Manufacturers have also used shock absorbent pads and other similar methods to alleviate the effects of mechanical shock. While these methods have proven effective in reducing minor frequency changes, a solution is not available to remedy substantial shift and perhaps total failure.
In radio communication devices where compliance with regulations set forth by various communication agencies is mandatory for operation, much less frequency shift is tolerable. Indeed operation of such devices is prohibited beyond a certain frequency shift.
In many situations the users of radio communication devices lose contact with the base or other users due to substantial frequency shift or component failure in the oscillator circuit without any prior notification. This loss of contact may prove detrimental and even hazardous in applications such as the public safety market.
Accordingly, a need exists for a method to recognize significant frequency shift in oscillator circuits and to prevent the total failure of the devices containing such circuits due to such shifts.